1. Field of the Invention
The present invention relates to an exhaust gas flow control valve for an internal combustion engine. The flow control valve according to the present invention is arranged in the exhaust pipe of the internal combustion engine. Moreover, this flow control valve adjusts the flow rate of exhaust gases so as to control numbers of turning revolutions of a turbocharger arranged at the upstream position of exhaust gas flow.
2. Description of the Prior Art
In the prior art, an exhaust gas flow control valve B0 of this kind is equipped, as shown in FIG. 1, with a body 1, a diaphragm actuator 5 and a bracket 9.
The body 1 is arranged in the not-shown exhaust pipe. On the other hand, the body 1 is formed with an exhaust passage 1a. A valve member 2 is arranged in the exhaust passage 1a. The body 1 supports a valve shaft 3. This valve shaft 3 has its one end connected to an arm 4. This arm 4 is connected to the rod 7 of the diaphragm actuator 5 by means of a pin (although not shown) (as disclosed in Japanese Utility Model Laid-Open No. 55-106342).
The diaphragm actuator (as will be shortly referred to as the "actuator") 5 has a casing 6. In this casing 6, there is arranged a diaphragm 8 which partitions the inside of the casing 6 into two chambers.
The lower chamber 5B of the casing 6 is vented to the atmosphere. On the other hand, the upper chamber 5A of the casing 6 is connected with a not-shown pressure source. This pressure source boosts the internal pressure of the upper chamber 5A when the accelerator pedal is depressed. Moreover, the pressure source moves the rod 7 downward together with the diaphragm 8. Reference numeral 10 designates a coil spring.
In this flow control valve B0, moreover, the bracket 9 holds the casing 6 of the actuator 5. The bracket 9 is connected and fixed to the body 1 by means of bolts 11. Numeral 12 designates bolts to be used when the bracket 9 fixed in the casing 6.
In this flow control valve B0, the internal pressure of the upper chamber 5A of the actuator 5 is dropped if the not-shown accelerator pedal is released Then, the rod 7 is moved upward together with the diaphragm 8 by the urging force of the coil spring 10. And, the valve shaft 3 is rotated by the arm 4. As a result, the valve member 2 closes the exhaust passage 1a. Thus, this flow control valve B0 adjusts the flow rate of exhaust gases.
In the flow control valve B0 of the prior art, however, the heat resistance of the diaphragm 8 of the actuator 5 is low (at about 200.degree. C. or lower). This makes it necessary to prevent the heat of the body 1 from being transferred through the bracket 9 to the diaphragm 8.
For this necessity in the prior art, the bracket 9 is connected and fixed to a cold portion of the body 1. This reduces the degree of freedom for arranging the bracket 9 in the body 1. As a result, the degree of freedom for mounting the flow control valve B0 in the internal combustion engine.
Incidentally, another solution can be made by constructing the flow control valve, as shown in FIG. 2. In this flow control valve B1, the bracket 9 is fixed on a peripheral device X separate from the body 1 by making use of the bolts 11.
According to this structure, however, the assembling accuracy and performance of the flow control valve B1 are dropped. This is because the individual parts of the actuator 5 have to be fixed in different positions. Specifically, the rod 7 for actuating the valve member 2 is connected to the side of the body 1, whereas the bracket 9 for holding the casing 6 is connected to the peripheral device X.
In the structure according such solution, moreover, the flow control valve B1 has its vibration resistance dropped. Specifically, the portion of the exhaust pipe to be arranged with the body 1 and the portion of the peripheral device X to be arranged with the actuator 5 have different intrinsic numbers of vibrations. As a result, the connected portions of the arm 4 and the rod 7 are displaced after a long use. And, this displacement may possibly cause failures of the flow control valve B1.